Introduction

Hanuman langurs (Presbytis entellus) have been among the first primate species where infanticide by adult males was observed and reported in the wild (at Dharwar, Sugiyama 1965; at Jodhpur, Mohnot 1971; at Abu, Hrdy 1974). Most cases were reported for hanuman langurs living in one-male groups (e.g., Sugiyama 1965; Mohnot 1971; Hrdy 1974, 1977; Newton 1986; Sommer 1994) and they usually took place after the resident male was replaced by a new immigrant. The occurrence of infanticide in hanuman langur multimale groups was first mentioned in 1980 by Ripley and has recently been documented in detail for a wild population at Ramnagar/Nepal (Borries 1997). Other studies on wild primate multimale groups confirmed that infanticide occurs in multimale groups (e.g., Papio ursinus, Busse & Hamilton 1981, see also Palombit et al. 1997; Alouatta seniculus, Crockett & Sekulic 1984; Macaca fascicularis, de Ruiter et al. 1994).

Generally, it is expected that the risk and frequency of infanticide should be lower in multimale groups as compared with one-male groups (e.g., Hrdy & Hausfater 1984; Leland et al. 1984; Altmann 1990; Newton & Dunbar 1994; Sommer 1994; van Schaik 1996). This is indeed supported by fewer infanticides in multimale groups of mountain gorillas (Robbins 1995), a low prevalence of infanticide in populations of hanuman langurs with a predominating multimale structure (Newton 1988; but see Sterck 1999) and low rates of infanticide in most baboon and macaque species (van Schaik, Chapter 2).